1. Field of the Invention
This invention relates to steering assemblies and more particularly to a boot seal for said steering assemblies having a molded attachment point for a fluid transfer tube.
2. Prior Art
Steering gear assemblies, particularly of the rack and pinion type, incorporate a tubular body member through which a rack bar projects out of the open ends of the tubular member. In order to seal the open end of the member, and to seal the area of the rack bar which is allowed to move in and out of the tubular member, a boot seal is generally provided, the boot having one axial end thereof sealingly attached in circumferential engagement with the bar or a tie rod attached to the end of the bar and the other end thereof sealingly attached in circumferential engagement with the tubular member. The seal is generally of the boot or bellows type which can accommodate both axial movement and lateral movement of a tie rod with respect to the tubular member. Oftentimes the tubular member terminates in a movable joint member interiorly of the seal, the movable joint member attaching the rack bar to a tie rod in an articulatable joint. Incorporating the joint interiorly of the seal allows the boot seal to function as a protective cover for this joint. Therefore, the seal must be able to accommodate both axial movement of the rack bar and lateral movement of the tie rod with respect to the rack bar.
As the rack bar moves axially, during steering, the bellows or boot seal must accommodate expansion and contraction of its inner dimensions. In order to allow this, while maintaining a seal, it is necessary to provide for escape of fluid pressure from the interior of the seal.
In some embodiments, this has been accomplished by allowing the pressure to move through the tube which receives the rack bar from one axial end thereof to the other. However, in certain rack and pinion steering assemblies, particularly power steering assemblies, it is not feasible to allow fluid movement from one end of the rack tube to the other. Specifically in power steering assemblies, portions of the rack tube are used as the power cylinder and the presence of a moving piston around the rack bar sealed against the inner diameters of the rack tube prevents fluid pressure transference along the interior of the rack tube.
It has been suggested, in those cases, to provide a separate fluid transfer tube extending from one boot seal to the other so as to accommodate pressure balancing between the two seals. Generally when one seal is collapsing, the other is expanding and therefore, the provision of a transfer tube communicating the interior of the two seals allows for pressure balancing in the seals without leakage to the exterior of the system.
Heretofore, most transfer tubes have terminated in fitted connections with bores through the end housings supporting the rack tube. Portions of these end housings form the attachment point for the rack tube associated end of the boot seal. Oftentimes, one of the end housings can comprise a portion of the pinion housing. The use of housing bores to communicate the interior of the seals with the interior of the tube requires considerable machining of the housing units to provide a bore from the exterior thereof to the end thereof interiorly of the attachment point of the boot seal to the housing member. This machining adds greatly to the expense of the steering system.